NASA's Curiosity rover analyzes Martian soil for the first time (pictures)

Sampling the soil of the red planet

From its primary excavation location on Mars, NASA's Curiosity rover has for the first time sampled the soil on the red planet. Although NASA has not yet found any organic compounds, it did find a complex chemistry of water, sulfur, and chlorine-containing substances.

Curiosity is the first Mars rover able to scoop soil into analytical instruments, and the tests have demonstrated the rover's scientific capabilities to analyze rock samples, something that's expected to continue for the next two years. These initial tests came from a drift of windblown dust and sand called "Rocknest," seen here, which is inside Gale Crater and still miles away from the rover's main destination on the slope of a mountain called Mount Sharp.

Analyzing gasses emitted from the samples heated in its tiny oven, the Sample Analysis at Mars (SAM) suite and the Chemistry and Mineralogy (CheMin) instrument found the composition is about half common volcanic minerals and half non-crystalline materials such as glass. SAM added information about ingredients present in much lower concentrations and about ratios of isotopes, which can provide clues about environmental changes.

Curiosity's work site

NASA's Curiosity Mars rover documented itself in the context of the "Rocknest Wind Drift" work site on the 84th Martian day, or sol, of its mission, October 31. The rover worked at this location from October 2 to November 16.

This mosaic of 55 images from the Mars Hand Lens Imager (MAHLI) shows the first four of five places from which the rover’s scoop obtained sand to clean the sample handling and processing system.

The rover’s robotic arm isn't visible in the mosaic because the MAHLI that took this mosaic is on the turret at the end of the arm.

Scoop marks in the sand at 'Rocknest'

The third and fourth trenches dug by NASA's Mars rover Curiosity during soil sampling are seen here in an image captured by the Mars Hand Lens Imager (MAHLI) on October 31. The upper surface of the drift is covered by coarse sand grains approximately 0.02 to 0.06 inches in size which form a thin crust about 0.2 inches (0.5 centimeters) thick.

Beneath the thin crusted surface is finer sand, which is darker brown as compared with the dust on the surface.

Windblown sand from the 'Rocknest' drift

The Mars Hand Lens Imager (MAHLI) on NASA's Mars rover Curiosity acquired closeup views of sands in the "Rocknest" wind drift to document the nature of the material that the rover scooped, sieved, and delivered to the Chemistry and Mineralogy Experiment and the Sample Analysis at Mars in October and November.

This photo shows some of the variety of coarse sand grains observed on a portion of the Rocknest wind drift. The sample shows translucent grains, gray and white sand, in addition to two blue-gray glassy spheres and a glassy ellipsoid. The spherical and ellipsoidal grains were likely formed from molten droplets that cooled above the Martian surface to form glass, either during an explosive volcanic eruption or an impact cratering event. Similar grains are found in association with impacts on Earth and explosive volcanoes on the moon. The larger glassy sphere is 0.026 inches in diameter.

A sampling of Martian soils

Previous NASA Mars missions, including the Viking, Pathfinder, and Mars Exploration Rover, have studied Martian soils, and now Curiosity has used its X-ray spectroscopy. Similar soil types have been observed at all landing sites, as well as during the overland travels of both Mars Exploration Rovers.

The Mars Exploration Rover Spirit's landing region in Gusev Crater is seen in both pictures at top; Viking's landing site is shown at lower left; and a closeup of Curiosity's Gale Crater soil target, called "Portage," is at lower right.

In Gusev Crater, several white subsurface deposits were excavated with Spirit's wheels and found to be either silica-rich or hydrated ferric sulfates.

Inspecting soils across Mars

This graph compares the elemental composition of typical soils at three landing regions on Mars: Gusev Crater, where NASA's Mars Exploration Rover Spirit traveled; Meridiani Planum, where Mars Exploration Rover Opportunity still roams; and now Gale Crater, where NASA's newest Curiosity rover is currently investigating. The data from the Mars Exploration Rovers are from several batches of soil, while the Curiosity data are from soil taken inside a wheel scuff mark called "Portage" and examined with its Alpha Particle X-ray Spectrometer (APXS).

Heating Martian sand grains

NASA's Mars rover Curiosity has sampled the soil and heated the specimens in order to release gasses. Heating fine-grained samples in the Sample Analysis at Mars (SAM) instrument has released water vapor, carbon dioxide, oxygen, and sulfur dioxide.

SAM has three instruments for analyzing gas from samples heated to different temperatures: a quadrupole mass spectrometer (QMS), a gas chromatograph (GC), and a tunable laser spectrometer (TLS). Together, they are capable of obtaining the composition of gases; identifying different isotopes of lighter elements; and detecting organic, or carbon-containing, materials if present.

Atmospheric loss on Mars

This plot shows the first-ever look at the deuterium-to-hydrogen ratio measured from the surface of Mars, as detected by the Sample Analysis at Mars (SAM) instrument on NASA's Curiosity rover.

Deuterium is a heavier version of the hydrogen atom. Scientists look at the deuterium-to-hydrogen ratios on Mars, along with isotopes of other elements, to understand how the atmosphere has changed over time. Mars, which has less gravity than Earth and lacks a strong enough magnetic field to shield its atmosphere from the sun, is slowly losing its atmosphere. As this process occurs, the lighter hydrogen atoms are preferentially lost compared with the heavier deuterium ones.

SAM measured the D/H ratios in water released when "Rocknest" sand samples were analyzed, and these samples show the water vapor consists of more deuterium than that of Earth's water -- i.e., the water is heavier. This is to be expected since the lighter hydrogen atoms in the Martian atmosphere are escaping faster than the heavier ones.

Signs of erchlorates and sulfur-containing compounds

NASA's Mars rover Curiosity has detected sulfur, chlorine, and oxygen compounds in fine grains scooped by the rover at a wind drift site called "Rocknest." The grains were heated and analyzed using the rover's Sample Analysis at Mars, or SAM, instrument suite. Scientists indicate the oxygen and chlorine may come from perchlorate or similar compounds, which contain chlorine and oxygen. Perchlorates were also found by NASA's Phoenix Lander at a different location on Mars. The sulfur compounds suggest the presence of sulfides or sulfates in the grains.

Chlorinated compounds at 'Rocknest'

Contrary to the excitement swirling last week after NASA said the organic compound seeking instrument, SAM, has found something very exciting, NASA has detected no Martian organic molecules at this point. Organic molecules are carbon-containing compounds essential for life on Earth.

The instrument did detect simple chlorinated carbon compounds, represented by ball-and-stick models on the graph. These compounds contain hydrogen and carbon as well as chlorine. More work is needed to determine if the carbon in these molecules is of terrestrial or Martian origin. The chlorinated compounds were likely created from a reaction with perchlorate or a perchlorite-like phase and carbon-containing molecules.

Curiosity rover's traverse

This map shows the places inside the Gale Crater where NASA's Mars rover Curiosity has driven since landing at "Bradbury Landing," and traveling to an overlook position near "Point Lake", covering 1,703 feet. Curiosity was at the easternmost marker on this map on November 30, where it sampled soils at the "Rocknest" location. The place called "Glenelg" is where three types of terrain meet. The depression called "Yellowknife Bay" is a potential location for selecting the first target rock for Curiosity's hammering drill.